Woman become less trusting when given the male hormone testosterone.

Scientists have discovered that the hormone testosterone, which makes men physically strong and aggressive, seems also to be connected to cynicism and a lack of trust in others.

They found that when it was given to women it appeared to “harden them up” and made them less open and more vigilant.

Historically for women it was important to be co-operative and sociable in order to survive whereas for men it was more important to be able to fight.

Men therefore evolved with more testosterone than women in order to make them bigger, stronger and more aggressive. It also seems to have made them more wary and to constantly “watch their back” for danger.